1. Field of the Invention
This invention relates in general to germ-killing compositions, methods of preparing and using same, and in particular to such compositions advantageously adapted for use in a wide variety of cleaning, sanitizing and disinfecting applications.
2. Description of the Prior Art
The use of chlorine compounds in various types of cleaning, sanitizing disinfecting, etc., compositions is of course well established. Chlorine compounds suggested for use in this regard include, for example, sodium hypochlorite, used in World War 1 as a wound irrigant, and chlorinated phenols such as m-chlorophenol, these compounds having increased bactericidal activity and reduced toxicity, in some instances, when compared to non-chlorinated phenols. Thus, m-chlorophenol has a phenol coefficient of 7.4 (B. typhosus), 5.8 (S. aureus). Other chlorine compounds found advantageous in some form of germ-killing utility include, without necessary limitation, chlorine gas itself, chlorine dioxide, chloramine T, mercuric chloride, calcium hypochlorite (a standard swimming pool disinfectant), chlorapicrin (an exterminator), chloroform (a fumigant) chloradane (an insecticide) zinc chloride (a preservative) and chloromycetin (an antibiotic).
Chlorine dioxide in particular has been found to be an especially effective germ killer. This compound is quite versatile and has long been used as a bleaching agent such as in the oxidizing of the natural colorant present in cotton, wood pulp and other cellulosic fibrous material. Thus, the chlorine dioxide, though performing an oxidizing function, is nevertheless non-injurious with respect to the fibrous material. Additionally, chlorine dioxide has long been used in the treatment of water supplies and is currently available commercially in powder form for use in swimming pools and in liquid form for household and industrial cleaning and disinfecting. In general, chlorine dioxide is superior to gaseous chlorine in the removal of odors, tastes and in destroying and removing algae or other organic material. Moreover, chlorine dioxide is considered at least as effective if not superior to chlorine gas as a bactericide, viruside or sporicide. Chlorine dioxide is further advantageous in that its antiseptic properties are not as sensitive to PH as chlorine i.e. chlorine dioxide retains its germ killing capacity to a significantly greater extent and over a wider PH range than does gaseous chlorine.
Despite the manifold advantages obtainable with the use of chlorine dioxide for the aforedescribed and related purposes, certain difficulties are nevertheless encountered in practice. Thus, chlorine dioxide as a concentrated gas is explosive and poisonous and accordingly is usually not shipped in the gaseous state to the medium or small user. It has thus become common practice to employ a chlorine dioxide-liberating compound such as sodium chlorite powder which is much safer from the standpoints of storage, shipping and handling. Generation of the chlorine dioxide from the parent sodium chlorite is usually effected in one of three ways as represented as follows:
(1) addition of acid EQU H+ + NaClO.sub.2 .fwdarw. HClO.sub.2 + Na+; 5 HClO.sub.2 .fwdarw. 4 ClO.sub.2 + HCl + 2 H.sub.2 O
(2) addition of bleach (hypochlorite) EQU 2 NaClO.sub.2 + NaClO + H.sub.2 O .fwdarw. 2 ClO.sub.2 + NaOH + NaCl
(3) addition of chlorine EQU 2 NaClO.sub.2 + Cl.sub.2 .fwdarw. 2 ClO.sub.2 + NaCl
The generation of chlorine dioxide, hereinafter designated also as ClO.sub.2, according to reaction (1) is generally effected with the use of relatively inexpensive inorganic acid eg; hydrochloric acid, sulfuric acid and the like. For home use, the use of phosphoric or acetic acid (vinegar) is sometimes indicated since they are comparatively safe to handle and generally readily available.
Acid-induced generation of ClO.sub.2 from sodium chlorite as heretofore recommended and practiced has proved ineffective for the most part. Thus, it is often found that the acid material utilized tends to react with the ClO.sub.2 evolved thereby reducing the effective amount of active ingredients available for useful purposes. In addition, the composition resulting from acidification of the sodium chlorite does not usually exhibit the desired germ-killing efficacy, and particularly from the standpoint of rate of germ kill. To compensate for this deficiency, it becomes necessary to use increased concentration of sodium chlorite and acid which can lead to toxicity problems and particularly when the composition is used in an enclosed air space. Another problem stems from the fact that the composition obtained from the interaction of the sodium chlorite and acid material does not provide a truly effective solvent medium for the active chlorine containing byproducts such as ClO.sub.2, chlorous acid and the like. Inhalation of these gaseous components to any significant extent can of course be injurious to health and thus the risk to personal safety becomes an important factor. Significantly, the toxicity problem imposes severe limitation on the general utility of the disinfectant composition and particularly with respect to treatment of human beings.